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it <br /> Chevron #9-8632 September 2014 <br /> 525 West Grant Line Road , Tracy <br /> Claim No: 9662 <br /> groundwater are not threatened, and it is highly unlikely that they will be, considering these factors <br /> in the context of the site setting . <br /> Rationale for Closure under the Policy <br /> • General Criteria : The case does meet all eight Policy general criteria. It is not conclusive <br /> whether secondary sources have been removed to the extent practicable in the former gasoline <br /> UST and dispenser areas. <br /> • Groundwater Specific Criteria: The case meets Policy Criterion 1 by Class 1 . The contaminant <br /> plume that exceeds water quality objectives is less than 100 feet in length. There is no free <br /> product. The nearest water supply well or surface water body is greater than 250 feet from the <br /> defined plume boundary. <br /> • Vapor Intrusion to Indoor Air: This case meets Policy Criterion 2b . Although no document <br /> titled 'Risk Assessment' was found in the files reviewed , a professional assessment of site- <br /> specific risk from potential exposure to petroleum constituents was performed by Fund staff. <br /> The assessment found that there is no significant risk of petroleum vapors adversely affecting <br /> human health . Although two soil vapor sample results in 2010 did not meet the Policy criteria, <br /> the sampling locations were in open areas. The only structure at the Site is a mobile office <br /> trailer with crawl space below the structures floor. Soil vapor intrusion, if any, would dissipate <br /> before reaching indoor space . Therefore, the pathway is incomplete. <br /> • Direct Contact and Outdoor Air Exposure : This case does not meet Policy criteria because <br /> historically several soil sampling results from six feet below surface (likely above groundwater <br /> table) did not meet Policy Table 1 , and current shallow soil conditions in the former gasoline <br /> UST and dispenser areas are unknown . <br /> Objections to Closure and Responses <br /> According to the Path to Closure page in GeoTracker, finalized on September 2, 2014, the County <br /> objects to UST case closure because: <br /> Secondary source remains. <br /> RESPONSE: We agree it is not conclusive whether secondary sources have been removed to <br /> the extent practicable in the former gasoline UST and dispenser areas. <br /> ® The case does not meet Policy vapor criteria . <br /> RESPONSE: This case meets Policy Criterion 2b. <br /> ® The case does not meet Policy direct contact criteria. <br /> RESPONSE: We agree. <br /> Recommendation <br /> The Fund recommends that the County direct the responsible party to conduct a shallow soil <br /> assessment at the Site to evaluate the current conditions and implement focused remediation if <br /> warranted. <br /> •�'�� /o ao� ld � <br /> KirlYtarson, P.G . Date Robert Trommer, C. H.G. Date <br /> Engineering Geologist Senior Engineering Geologist <br /> Technical Review Unit Chief, Technical Review Unit <br /> (916 ) 341 -5663 (916 ) 341 -5684 <br /> Page 2 of 2 <br />